Why NAS Might Overtake SAN Storage

Not only might NAS replace SAN in the coming world of Ethernet-based storage, but the distinctions between the two might also disappear.

The following words were written on this site back in 2002, when Drew Bird was writing about the basics of storage area networks (SANs).

"Many IT organizations today are scratching their heads debating whether the advantages of implementing a SAN solution justify the associated costs. Others are trying to get a handle on today's storage options and whether SAN is simply Network Attached Storage spelled backwards."

Truer words could not have been written, and they still ring true today. I am fond of saying that there are no new engineering problems, just new engineers solving old problems. Today SAN and NAS still dominate the market. Many of the tradeoffs are the same, but change is coming.

Feature/function

NAS

SAN

Performance scalability

NAS performance does not scale, but change is on the horizon

Scalable performance at the hardware layer and now scalable for clients with shared file systems

Size scalability

Most NAS systems do not scale, but change is coming

SANs scale to hundreds or thousands of nodes

Management

All NAS systems are easy to use or they could not make it in the market

SANs are still hard to use; SNIA standards to solve this have never come to fruition

Cost

NAS systems are generally far less costly per GB and for people to manage

SAN systems are generally far more costly to operate

While not much has changed in the nearly eight years since that article was written, there are some big changes on the way, particularly for NAS:

The introduction of NFSv4.1 (pNFS) has the potential to put NAS performance on a par with SAN. NAS vendors are going to have to change their file systems to provide better scalability, however. Up to now, between the performance limitations of NFS and Gigabit Ethernet speeds, it was not important for vendors to have scalable file systems.

With SAN shared file systems, sharing data from multiple machines in a SAN is now possible. It was not possible to easily share data across SANs in 2002, because shared file systems were in their infancy.

Technological Change Favors NAS

If you combine NFSv4.1, 10GbE and a scalable NAS file system, the three combined could make SANs a thing of the past. Why would anyone want to use more expensive, more complex technology with less functionality and a more difficult management framework? Obviously, the answer is no one. SAN shared file systems can easily be changed to NAS file systems. The key will be if the major NAS vendors upgrade their file systems to support the new high data transfer world becoming available on NAS.

iSCSI up until recently was not very popular, as it did not provide much in the way of performance benefits. This is changing, and more high-end storage vendors are now supporting iSCSI. With 10GbE pricing dropping fast and FCoE NICs available in the market, I suspect iSCSI will become more popular and another option for a large variety of storage systems.

In the near future, the real distinction that will need to be decided is what is a SAN connection and what is a NAS connection. Is iSCSI over 10GbE to a storage system with a file system a NAS connection, or is iSCSI over 10GbE to a storage system where the file system is on the server a SAN connection? Is Fibre Channel over Ethernet SAN or NAS?

Clearly, the lines between SAN and NAS are being blurred. Some might say NAS is where you communicate with NFSv4.1 (pNFS), as that means you are communicating over a network. Some might say SAN is where the file system resides on the host and the communication using 10 GbE and TCP/IP does not make it a NAS connection.

The bottom line is it does not matter much anymore. SAN and NAS are close to convergence and what matters is cost and complexity. You are not going to be able to swap out 15 years of SAN technology in the current economic environment. On the other hand, 10 GbE prices are far lower than Fibre Channel pricing and a number of vendors are making 10 GbE to Fibre Channel switches that allow for extra connectivity to legacy hardware. This allows you to make the transition from Fibre Channel to 10 GbE using your legacy storage hardware. As someone who was around working on early SAN hardware in the mid-1990s, it is exciting to see the changes in the market and the convergence to a single network for both storage (SCSI, FCoE, iSCSI and so on) and external communication (TCP/IP LAN and WAN).

No matter what your job is today, you are going to have to learn something new. The days that companies had a SAN and a LAN group are going to come to an end soon, and the days that these groups fought over who will deploy NAS is going to come to an end too. We are all going to have to work with the singe fabric of the future. I have been in the industry for three decades and have seen the infighting between the LAN/WAN people and the storage people in organizations get pretty bad. We are all going to have to work together to plan the same SAN/LAN box.